The central message of this sermon is that one person, often overlooked or underestimated, can have a profound impact on transforming an entire situation through their faith and obedience to God's call. This is illustrated through the stories of David and Goliath, John the Baptist, and Jesus' birth. The speaker emphasizes that it's not about individual greatness or accomplishments, but about surrendering to the power of the Holy Spirit and pointing others to Jesus. This idea advances the belief that faith and obedience are essential in God's plan of salvation, and that even ordinary people can play a significant role in His story. The takeaway for listeners is that they too can be agents of change, not by their own strength or wisdom, but by trusting in the power of the Holy Spirit to guide them and transform others through their lives.